The present disclosure relates to a display unit, a manufacturing method thereof, an organic light emitting unit, and a manufacturing method thereof. The present invention particularly relates to a surface light emitting type display unit, in which light emitting devices such as an organic EL device are arranged and formed on the substrate and a desire light emitting color can be selectively extracted, a manufacturing method thereof, an organic light emitting unit, and a manufacturing method thereof.
In recent years, as a display unit taking the place of the cathode ray tube (CRT), research and development of light weighted and small flat display units with small electric power consumption has been actively implemented. Of the foregoing, a display unit using an organic light emitting unit including a self-light emitting display device (so-called light emitting device) such as an inorganic EL device and an organic EL device attracts attention as a display unit capable of being driven with low electric power consumption.
As a configuration for providing a full-color display unit using such light emitting devices, for example, (1) a configuration in which light emitting devices for emitting blue light, green light, and red light are arranged, (2) a configuration in which a color conversion filter is combined with a white light emitting device or a blue light emitting device and the like have been proposed.
Of the foregoing, in the configuration (1), a configuration in which high efficiency by interference of light extracted from each light emitting device is attained by adjusting the film thickness of the transparent electrode on the glass substrate on the light extraction side for every blue, green, and red light emitting device has been further proposed (refer to Japanese Unexamined Patent Application Publication No. 2003-142277).
Further, in the configuration (1), it is proposed that a light emitting device structure in which a function layer including a light emitting layer is sandwiched between a reflecting electrode and a semi-transparent material layer is adopted, and a resonator structure in which light generated in the light emitting layer is multiple-interfered between the reflecting electrode and the semi-transparent material layer and is extracted from the semi-transparent material layer side is used. By adopting such a configuration, color purity of extracted light can be improved, and extraction intensity in the vicinity of the central wavelength of resonance can be improved. Therefore, in the display unit in which light emitting devices having the peak in the respective blue, green and red wavelengths are arranged in parallel, when the display unit is structured by setting the optical distance of the resonator structure in the respective light emitting devices according to the wavelengths of extracted light from the respective blue, green, and red light emitting devices, improvement of front luminance and improvement of color purity have been attained. Further, by extracting emitted light through color filters, high quality display units with still higher color purity and small view angle dependence, in which contrast lowering due to panel surface reflection is prevented has been attained (refer to International Publication No. WO01-039554).
For the configuration for obtaining a full-color display unit using light emitting devices, some related arts have been proposed. Specifically, in order to improve emission efficiency of light emitted from the light emitting devices, the technique to change, of the function layer including a light emitting layer, the thickness of layers other than the light emitting layer for each color has been known (refer to Japanese Unexamined Patent Application Publication No. 2000-323277). In the configuration, based on the difference in thickness among layers other than the light emitting layer, that is, based on the difference in light path lengths in the light emission process, light emission efficiency is improved for every color by utilizing light interference phenomenon. Further, in order to lower resistance of the electrode layer (transparent electrode), the technique to insert a metal film (for example, silver (Ag) being 50 nm or less thick) in the electrode layer has been known (refer to Japanese Unexamined Patent Application Publication No. 2002-324792). In the configuration, resistance of the electrode layer is lowered by utilizing conductivity characteristics of the metal thin film. Further, in order to effectively generate high-luminance white light, the technique in which a light emitting layer is structured by layering a blue light emitting layer for generating blue light, a green light emitting layer for emitting green light, and a red light emitting layer for generating red light has been known (refer to Japanese Unexamined Patent Application Publication No. H10-003990). In the configuration, based on the structural characteristics of the light emitting layer structured by layering the blue light emitting layer, the green light emitting layer, and the red light emitting layer, white light luminance is improved, and generation efficiency of the white light is improved.
However, in the foregoing configuration according to (1), since the respective light emitting devices for emitting blue light, green light, and red light are arranged on the substrate, the light emitting layer and the function layer including the light emitting layer in the light emitting device of each color should be respectively formed. For example, when organic EL devices are used as a light emitting device, not only the light emitting layer, but also the function layer of the electron injection layer, the electron transport layer, the hole injection layer, and the hole transport layer should be respectively designed according to the light emitting layers in some cases. Therefore, designing and forming the function layer in the light emitting device of each color have been very complicated. Further, in manufacturing such a light emitting device, the function layer including the light emitting layer is pattern formed by vapor deposition or coating using a metal mask, furthermore by inkjet. However, when vapor deposition or coating using a metal mask is performed, there is a limit of alignment accuracy of the metal mask. When inkjet is used, there is a limit of the patterning precision. Therefore, it is hard to miniaturize and jumboize the light emitting device and space between the light emitting devices. Further, the foregoing limits are the cause of preventing realization of the display unit capable of higher definition display.
Meanwhile, in the configurations of (2) and (3), since light in the same wavelength region may be emitted in each light emitting device, it is not necessary to separately form the function layer including the light emitting layer for every color. Therefore, the manufacturing steps including designing each light emitting device is simpler than of the configuration according to (1). However, in the configuration of (2), the color filter absorbs unnecessary light emitting component, and therefore light emission efficiency is lowered, leading to large load on the electric power consumption and device life. Further, it is difficult to provide filtering white light emission in the light emitting device into blue, green, and red with favorable color purity by transmission characteristics of the color filters capable of being mass-produced, and only the display unit in which the extracted light has a wide wavelength distribution and poor color reproducibility can be produced. Further, in the configuration of (3), there are problems of low conversion efficiency of the color conversion filters, difficulty of manufacturing the color conversion filters, life of the color conversion filters, color purity of emitted light colors after color conversion and the like, and therefore it is hard to put the configuration in practical use.